Questions tagged [digital-communications]
Related to all communication systems that use a given digital sequence as an interface between the source and the channel input.
377
questions
1
vote
1answer
74 views
optical glow fiber for low-tech communication links?
Can cheap "glow" optical fiber (or other inexpensive materials such as aquarium air tubing, etc.) be used for low-tech low-speed optical communications using just simple discrete components, such as ...
5
votes
2answers
2k views
RX vs TX operation in Software UART
I am short of 1 UART in my MCU. I needed 4 but so far what I have found suitable is an MCU that has 3 UARTs in it, STM32F103. So the 4th one I will have to implement in SW.
Each of my individual ...
0
votes
0answers
78 views
CAN Sniffing - is my approach flawed? [on hold]
I'm working on an automotive project to sniff CAN data and reverse engineer PIDs.
The project is based on a ChipKit Max32 & Network Shield - chosen for its dual channel CAN controllers. The idea ...
0
votes
0answers
25 views
RSS/RSSI Applications? [closed]
What are the applications of knowing RSSI as an absolute value or as a relative value? I know the importance of this in estimating distance for Indoor localization, but, what else can you think of?
...
0
votes
0answers
54 views
Trouble connecting to temperature controller using MODBUS,RS485 and MATLAB
I am trying to communicate with a temperaturature controller ATR-401 using MATLAB but i am having trouble just connecting to it and reading temperature data.I have set baud rate, data bits, parity and ...
-2
votes
0answers
24 views
User Bandwidth and Throughput in mmWave?
I would like to calculate the maximum achievable throughput for a user in downlink communication in the mmWave band. I know that the Shannon's Capacity equation can be used for this, but to use it I ...
2
votes
1answer
103 views
What is this radiation coming from my phone?
I've built myself a crude EMI probe:
I then pointed it at the top part of my phone when the phone was powered on, and I saw the following waveforms on my scope.
First off, there are spikes every ...
0
votes
1answer
56 views
Shannon - Hartley Theorem
Let's consider the Shannon - Hartley formula for the channel capacity \$C\$:
$$C = B \log_2 (1 + S/N)$$
I have two doubts about it:
1) is it correct for TDMA, FDMA, or CDMA? And why?
2) Can a ...
0
votes
1answer
54 views
Energy of a complex exponential signal
Noob question here. Why would the term \$j2\pi t\$ not have any effect on the energy of the signal?
0
votes
0answers
17 views
PAPR (Peak to average power ratio) of OFDM signals
Will the PAPR of an OFDM signal using QPSK modulation on its subcarriers be different than the PAPR of an OFDM signal using QAM256 on its subcarriers? assuming the same number of subcarriers
0
votes
0answers
27 views
Setting up parameters for generating QAM signals
I am trying to simulate multiple baseband QAM signals for random data at varying power levels, data-rate, carrier frequency, and modulation order using MATLAB. Here is how I set up the parameters:
<...
0
votes
0answers
40 views
Two-way communication between esp32s
I am planning a circuit that requires two-way communication between one esp32 and 3 others. I want to use a master/slave architecture as shown here:
They need to be able to communicated via hardware, ...
0
votes
1answer
53 views
8085 MPU; Stepping through an instruction (Timing diagrams)
Let me write the steps of ADD B, as I've understood it till now.
T0:
ALE goes high
Memory location(say \$2000_h\$) is taken from Program Counter to Memory Address Register(which points to the ...
2
votes
0answers
92 views
Vanishing of Gibbs Phenomenon in MatLab
I was trying to represent a square wave with its Fourier series in Matlab. But as I increased the number of terms in Fourier series expression, the Gibbs phenomenon vanished and the edges of the ...
0
votes
0answers
38 views
Need help in computing the evolution of symbol error rate for uncoded OOK scheme over fading channels
I am trying to reproduce the results exhibited in Fig. 1. in the reference, i.e., "Error performance of coded FSO links in turbulent atmosphere modeled by gamma-gamma distributions" linked to (https://...
-2
votes
1answer
54 views
Can anybody explain to me how to solve such questions? Constellation Diagram [closed]
i'm not able to proceed with such questions. If someone could explain how to solve such questions, would be a big help. Thanks.
0
votes
0answers
56 views
GBE (Gigabit Ethernet) Magnetic Coils Connection Order
I am designing a MEZ PCB and I need to connect the GBE coils to the assigned pins of single board computer's MEZ connector. My trouble is I do not want to use any more via for this connections. Hence, ...
0
votes
2answers
59 views
Preventing audio feedback in an underwater multiway intercom
I'm trying to transmit data(bytes) from a speaker (out) to microphone (in) via an FM modulated link. Now I have the problem that both will be used simultaneously (full duplex) and next to each other (...
1
vote
2answers
78 views
Is there a method to get the carrier from the recieved QPSK signal?
If we have given a signal and we know that is a modulated QPSK signal, can we recover the carrier if we know the carrier frequency fc.
Edit: A clarification, I do not have to do it in hardware, a ...
0
votes
0answers
19 views
How to perform multiplication at the time series level for chirp signals
As the title said: How to perform multiplication at the time series level for chirp signals?
In LoRa modulation, when received a chirp modulated signal, to demodulate it, LoRa will first multiple the ...
25
votes
13answers
4k views
Examples of fluid (including air) being used to transmit digital data? [closed]
We usually use electrons to communicate data across wires, and sometimes we use light also. Does anyone know of real world example systems that use fluids (including air) to do this, and the ...
0
votes
1answer
46 views
What is the transmission bandwidth for a BASK (Binary Amplitude Shift Keying) signal?
What is the transmission bandwidth for a BASK (Binary Amplitude Shift Keying) signal?
Shouldn't it be infinity as short periods of sinusoids are used to depict 1 and 0 to depict 0?
0
votes
0answers
26 views
CAN Transciever kbps to Hz at TXD Pin
I am new to the CAN Bus and have designed an application example. The Transceiver I have chosen is TJA1044Gx.
The transceiver data sheet says :
I want to know if I have only Transceiver, Analog ...
0
votes
2answers
69 views
Can we band pass filter QPSK signal?
Consider we have QPSK signal with carrier frequency 10kHz. Generally, we demodulate or use matched filter on the the QPSK signal and recover the transmitted bit or the symbols. If the QPSk signal is ...
1
vote
0answers
8 views
How is n_pucch_2 in rrc layer computed
In LTE network I know that n_pucch_2 is used to indicate the resource index for pucch format 2/2a/2b. And I know its value is defined in higher layer. But how is the value computed and defined in the ...
1
vote
1answer
39 views
What is the minimum sampling rate for QPSK or what is the bandwidth of QPSK signal?
Consider we have created a QPSK signal with a carrier frequency 100kHz. Before applying matched filter or demodulation we need to take sampls from the received signal. So what is the minimum sampling ...
0
votes
1answer
31 views
Machine comms troubleshooting
While this may be suited for an automotive section I believe my question is better suited to this forum.
I'm having OBD II comms issues and have a run a similar troubleshooting process to what's ...
0
votes
1answer
66 views
JSON for GSM Comm on STM32
I am making a remote monitoring system using STM32F1 MCU in which there are few digital and analog sensors attached and I would send their readings to a remote server periodically. Can I use JSON ...
3
votes
0answers
141 views
Strange I2C communication
I am currently trying to test the SHT3x series humidity sensors by Senserion. I have their EK-H4 evaluation kit to get data from the sensors. I can plug in the sesnsors provided with the kit, and all ...
0
votes
2answers
41 views
1-wire differentiate read from write
I've been reading documentation on 1-wire and I think I'm having a brainfart. How does the slave differentiate a read slot from a write slot?
reference:
https://www.maximintegrated.com/en/app-notes/...
1
vote
0answers
143 views
How to Low-Pass PDM Output Data
I have a PDM-Mems Microphone which provides me with 101010 data, the Microphone has a Clock of 3Mhz. I read the manual about how PDM is generated, but I haven't worked with digital filters yet and in ...
-1
votes
1answer
36 views
Pairing vs Master-slave between BT Module to BT Module
If I take two identical BT modules, for example HC05 or HC06 then is it possible to pair the two modules with each other or is it like you need 1 master and 1 slave module for pairing?
Edit:
Now I ...
-1
votes
1answer
73 views
Bluetooth vs BT Beacon [closed]
While trying to understand how BT devices work I came across another related term "BT Beacon". Is it same as BT communication or if a device is termed as BT beacon then it would have some specific ...
0
votes
0answers
49 views
What is the fieldbus for Unitronics PLC?
I am currently investigating the inner behavior of a PLC of the brand Unitronics. I identified several bus for the communication with actuators, other PLCs, etc (like Modbus or CANbus)
One thing I ...
0
votes
0answers
10 views
finding the minimal length of a broadcasting frame in a channel(CSMA/CD)
i am unsure about this question. would appreciate your assistance with it.
in the following CSMA/CD network with cable length L and propagation T. assuming that the signal is not decreasing and there'...
0
votes
2answers
87 views
Does direct GPIO communication between 2 microcontrollers requires pull up/down
If I want to use GPIO pins of two microcontrolles as a mean of simple communication (e.g. reporting an event by sending 1 or 0), Do I need to enable internal pull up or pull down resistors on any of ...
0
votes
0answers
88 views
Probing LPC bus with an FPGA yields gibberish — wiring problem?
I'm trying to repeat the TPM key dumping experiment by Pulse Security using a motherboard with Secure Boot and the same TPM1.2 chip onboard, equipped with Windows 8.
However, when I connect the FPGA ...
0
votes
1answer
59 views
Finding the overhead and distance of an unknown code based on message making algorithm
for an information word M with m bits that is coded as following:
M is coded into a word A using an unknown code that allows detection of not more than one error.
the code word is the word obtained ...
0
votes
1answer
16 views
loading multiple shift registers from few pins
We want to load two 32 bit data shift registers without concatenating them using 4 control lines (SI1, SI2 clock, latch). It can be done by bit banging but can it be done using SPIs using only 4 lines?...
0
votes
0answers
25 views
Find Bit Error Rate and Eb/N0?
I have read about Bit Error Rate and Eb/N0 to find out how can I generate them. I understand BER but what confused me is Eb/N0. How can I find Eb/N0 values and the corresponding BER values.
I have ...
1
vote
1answer
77 views
Signal placement in flat ribbon cable, FPC or FFC with digital and power signals
I want to interface different boards with FPC/FFC or ribbon cable and I was wondering about the placement of the signals in the cable.
I plan to have a 39 signals FPC with :
1 SPI bus (SCK, MOSI, ...
0
votes
1answer
53 views
Visualise a bit pattern
My objective is to send a bit pattern of 1000 bits from one microcontroller (PIC or Atmel) to another one using the SPI method.
How can I visualize the bit pattern so I can find the errors of ...
1
vote
1answer
39 views
Source generator for Satellite Tuner input
I need to design a source generator for a TV factory. They want to automatize the functional tests by applying a test module to the TV's at the end of the production line. All the peripherals of the ...
1
vote
1answer
44 views
What is the effect of redundancy coding on the bit error rate?
If I have a channel with bit error rate BER = \$10^{-3}\$ after modulation, but this is too high so I decide to add repetition coding. With 2 code words and block length of 3 such that I have a ...
0
votes
3answers
94 views
Choosing best bus and protocol for ~128 clients over the wire
I am up to design system with ~128 MCUs communicating to one MCU master. Communication will be bidirectional. Data will be mostly sensor reads, but I plan to use the bus also as communication method ...
0
votes
1answer
106 views
How do I stop signal looping with I/O port in this communication system
I am still a student. When I am designing communication system I am facing this problem: As shown in the figure I need to communicate with Master and Slave. But Master and Slave have single I/O port ...
2
votes
3answers
185 views
How is companding different from pre-emphasis and de-emphasis?
What I know is that interference increases linearly with frequency and thus noise power is concentrated at higher frequency. So, to reduce noise, pre-emphasis and de-emphasis filters are used which ...
-1
votes
1answer
303 views
Signed and unsigned numbers in verilog
I understand the concept of fixed point and multiplying signed with unsigned by sign extension the unsigned number with 1 bit of '0' so it will be signed always positive number, But my question
If I ...
0
votes
1answer
97 views
UART Transmit issue in VHDL
I'm working on a UART transmit process (uart_transmit) in VHDL (115200 baud, 8 data bits, 1 stop bit and no parity). I need the transmit line ...
0
votes
1answer
191 views
Are horizontal and vertical back porches required for digital video, and if so, why?
The necessity of vertical and horizontal front and back porches in analog video seem fairly intuitive to me, but why are they necessary for digital video at all? In this LCD module data sheet and this ...
